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Hellgren, Johan
Publications (9 of 9) Show all publications
Hellgren, J. (2002). Analysis of feedback cancellation in hearing aids with Filtered-X LMS and the direct method of closed loop identification. IEEE transactions on speech and audio processing, 10(2), 119-131
Open this publication in new window or tab >>Analysis of feedback cancellation in hearing aids with Filtered-X LMS and the direct method of closed loop identification
2002 (English)In: IEEE transactions on speech and audio processing, ISSN 1063-6676, E-ISSN 1558-2353, Vol. 10, no 2, p. 119-131Article in journal (Refereed) Published
Abstract [en]

Feedback cancellation in hearing aids based on Filtered-X LMS is analyzed. The data used for identification of the feedback path is the output and input signals of the hearing aid. The identification is thus done in closed loop. Tracking characteristics and bias of the optimal estimate are discussed. The optimal estimate can be biased when the identification is performed in closed loop and the input signal to the hearing aid is not white. It is shown that the bias could be avoided if the spectrum of the input signal was known and the data used to update the internal feedback is prefiltered. The effects of different choices of the design variables of the Filtered-X LMS are discussed. Three alternatives of the fixed filter were evaluated on feedback paths of hearing aids on human subjects and with alternative spectra of the input signal. The optimal estimate of the Filtered-X LMS with an individually adjusted fixed filter showed the best agreement with the desired estimate.

Keywords
Adaptive filters, Hearing aids, Identification, Least square methods
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-46978 (URN)10.1109/89.985549 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
Hellgren, J. & Forsell, U. (2001). Bias of feedback cancellation algorithms in hearing aids based on direct closed loop identification. IEEE transactions on speech and audio processing, 9(8), 906-913
Open this publication in new window or tab >>Bias of feedback cancellation algorithms in hearing aids based on direct closed loop identification
2001 (English)In: IEEE transactions on speech and audio processing, ISSN 1063-6676, E-ISSN 1558-2353, Vol. 9, no 8, p. 906-913Article in journal (Refereed) Published
Abstract [en]

The undesired effects of acoustic feedback of hearing aids can be reduced with an internal feedback path that is an estimate of the external feedback path. This paper analyzes the limiting estimate of the feedback for feedback cancellation schemes that apply some recursive prediction error method with a quadratic norm, e.g., least mean square (LMS) and recursive least squares (RLS), to the output and input signals of the hearing aid to identify the feedback path. The data used for identification is then collected in closed loop and the estimate used in one recursion will affect the data used in succeeding recursions. These properties have to be considered in the analysis. The analysis shows that the limiting estimate may be biased if there is an error in the used model of the input signal to the hearing aid, and that the system is not identifiable unless a second input signal to the system is added to the output of the hearing aid or the signal processing of the hearing aid used to modify the signal to the impaired ear is nonlinear. The limiting estimate is presented as the solution to an optimization problem in the frequency domain. An analytical expression of the limiting estimate is presented for a special case. For other cases an algorithm is presented that can be used to find a numerical solution. The results can be useful when the model structure used with the recursive identification is chosen.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-27807 (URN)10.1109/89.966094 (DOI)12554 (Local ID)12554 (Archive number)12554 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-12-13
Larsby, B., Johansson, M. & Hellgren, J. (2001). STAF i Örebro: Certifierade ingenjörer och skolan i centrum.. Audio Nytt, 28, 25-27
Open this publication in new window or tab >>STAF i Örebro: Certifierade ingenjörer och skolan i centrum.
2001 (Swedish)In: Audio Nytt, ISSN 0347-6308, Vol. 28, p. 25-27Article in journal (Other (popular science, discussion, etc.)) Published
Place, publisher, year, edition, pages
Stockholm: , 2001
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-63844 (URN)
Available from: 2011-01-04 Created: 2011-01-04 Last updated: 2018-05-21
Hellgren, J., Lunner, T. & Arlinger, S. (1999). System identification of feedback in hearing aids.. Journal of the Acoustical Society of America, 105, 3481-3496
Open this publication in new window or tab >>System identification of feedback in hearing aids.
1999 (English)In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 105, p. 3481-3496Article in journal (Refereed) Published
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-27619 (URN)12353 (Local ID)12353 (Archive number)12353 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-12-13
Hellgren, J., Lunner, T. & Arlinger, S. (1999). Variations in the feedback of hearing aids.. Journal of the Acoustical Society of America, 106, 2821-2833
Open this publication in new window or tab >>Variations in the feedback of hearing aids.
1999 (English)In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 106, p. 2821-2833Article in journal (Refereed) Published
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-27618 (URN)12351 (Local ID)12351 (Archive number)12351 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-12-13
Arlinger, S., Billermark, E., Öberg, M., Lunner, T. & Hellgren, J. (1998). Clinical trial of a digital hearing aid. Scandinavian Audiology, 27(1), 51-61
Open this publication in new window or tab >>Clinical trial of a digital hearing aid
Show others...
1998 (English)In: Scandinavian Audiology, ISSN 0105-0397, E-ISSN 1940-2872, Vol. 27, no 1, p. 51-61Article in journal (Refereed) Published
Abstract [en]

A clinical trial of Oticon DigiFocus hearing aid was performed. The test aid was evaluated on 33 subjects with several years' experience as users of modern analog hearing aids. These aids were used as reference for the 1-month-long trial. The Abbreviated Profile of Hearing Aid Benefit (APHAB) showed a mean difference in benefit with superior ratings for the test aid concerning ease of communication, speech in reverberation and speech in background noise. The subjects' own aids were rated somewhat better concerning aversiveness of sounds, but this difference was not statistically significant. The Gothenburg Profile showed a statistically significant difference between the test aid and the reference aids in favour of the test aid. The difference was not most evident with regard to speech communication and the effects of hearing loss on social interactions. Sound quality ratings concerning clearness were significantly higher for the test aid. Speech recognition thresholds in noise were on average 0.7 dB better for the test aids when tested at speech levels 60 and 75 dB. The difference was statistically significant only at 75 dB. There was significant interaction between general preference and hearing aid type, indicating that overall sound quality was an important factor affecting the general preference for either the test aid or the reference aid. Twenty-three subjects generally preferred the test aid, six preferred their own aid and four stated no difference.

Place, publisher, year, edition, pages
Taylor & Francis, 1998
Keywords
Hearing aid, digital signal processing, clinical trial, hearing aid benefit, speech recognitio
National Category
Medical Engineering
Identifiers
urn:nbn:se:liu:diva-156618 (URN)10.1080/010503998419704 (DOI)000071975600007 ()9505292 (PubMedID)2-s2.0-0031931465 (Scopus ID)
Available from: 2019-04-29 Created: 2019-04-29 Last updated: 2019-05-06Bibliographically approved
Lunner, T., Hellgren, J., Arlinger, S. & Elberling, C. (1997). A digital filterbank hearing aid: Predicting user preference and performance for two signal processing algorithms. Ear and Hearing, 18, 12-25
Open this publication in new window or tab >>A digital filterbank hearing aid: Predicting user preference and performance for two signal processing algorithms
1997 (English)In: Ear and Hearing, ISSN 0196-0202, E-ISSN 1538-4667, Vol. 18, p. 12-25Article in journal (Refereed) Published
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-40489 (URN)53369 (Local ID)53369 (Archive number)53369 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
Lunner, T., Hellgren, J., Arlinger, S. & Elberling, C. (1997). A digital filterbank hearing aid: Three digital signal processing algorithms-User preference and performance. Ear and Hearing, 18, 373-387
Open this publication in new window or tab >>A digital filterbank hearing aid: Three digital signal processing algorithms-User preference and performance
1997 (English)In: Ear and Hearing, ISSN 0196-0202, E-ISSN 1538-4667, Vol. 18, p. 373-387Article in journal (Refereed) Published
Abstract [en]

    

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-40488 (URN)53368 (Local ID)53368 (Archive number)53368 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
Arlinger, S., Larsby, B., Lunner, T. & Hellgren, J. (1994). Assessment of speech perception in noise using a conventional speech recognition and a subjective adjustment method.. Paper presented at XXII International Congress of Audiology 1994..
Open this publication in new window or tab >>Assessment of speech perception in noise using a conventional speech recognition and a subjective adjustment method.
1994 (English)Conference paper, Published paper (Refereed)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-63805 (URN)
Conference
XXII International Congress of Audiology 1994.
Available from: 2011-01-03 Created: 2011-01-03 Last updated: 2011-02-04
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